The present invention relates to an improvement in the profile of the outer surface of a pneumatic radial tire, particularly a heavy-load pneumatic radial tire.
In the case of a heavy-load pneumatic radial tire, a load applied per tire is high, which brings about various problems with respect to durability. Specifically, in respect of each portion of a tire, there exist various problems such as occurrence of separation at the belt edge of the belt portion, occurrence of peeling of cords in the carcass layer around the side portion from rubber surrounding the cords (cushion rubber and filler rubber), and occurrence of separation of the bead portion around the bead core thereof from the turn-up end of the carcass layer.
For this reason, although, for example, the so-called reinforcing layer (a chafer) has been provided in the prior art on the bead portion for the purpose of suppressing the occurrence of the separation in the bead portion, no satisfactory effect could be attained (see Japanese Patent Application Kokai Publication Nos. 49-902, 49-113303 and 50-63601).